I was searching for an article about a company who did a test, having their employees use the left hand for the mouse for several months, but I couldn't find it right now. However, I found this:

Ambidextrous tendencies may mean better memory.

Having a close left-handed relative makes right-handers better at remembering events than those from exclusively right-handed families, new research suggests. There is a downside, however, as members of these ambidextrous families may be relatively impaired in their ability to recall facts.

According to the study, having a left-handed sibling or parent means the organisation of your brain is intermediate between a pure 'lefty' and a pure 'righty'.

Specifically, Stephen Christman and Ruth Propper at the University of Toledo, Ohio claim that people with 'lefties' in the family have a larger corpus callosum - the connection between the brain hemispheres. This makes you better at certain memory tasks, but worse at others, they believe.

Two types of memories are involved. Episodic memories are those with a context that is separate from the information itself - for example, where you parked your car or where you left your keys. Semantic memories on the other hand are things 'you just know', such as the dates of the First World War or the recipe for apple pie.

Filling the gaps

The researchers showed 180 right-handed subjects lists of words. Some of this group was asked to recall as many of the words as possible once the list had been taken away. This tests episodic memory because the subjects have to remember the words they were taught.

Others from the group were given fragments of words with a letter missing and asked to fill in the gaps. This semantic test simply relies on knowing how the correct word should be spelt. Subjects with close left-handed relatives did better at the first 'remember' task, but worse at the second 'know' task.

"The key difference is not whether you are right handed, but whether you are strongly or weakly handed," explains Christman.

It's from New Scientist, and here's a link to another article:

Seems that cats tend to be left pawed.

http://www.geocities.com/Athens/Acro.../lefthand.html